Measurement of common mode noise in binary read-out systems

Estimators for the magnitude of common mode noise in a binary read-out system are studied using a simple Monte-Carlo program, and the theoretical background is explained. The occupancy per event is found to be a simple but very sensitive and specific test for common mode noise, which also leads to a quantitative measure of common mode noise. We introduce the observable Γ, which at 50% occupancy directly gives the common mode noise contribution. The autocorrelation function and the correlation matrix in addition provide information on the coherence length of common mode noise.